Operator is online while he stays on the "Visitors" page. There could be connection issues, thus we use the online time threshold to determine if the operator is online. If the server has "seen" an operator in the last 30 seconds (the default value), the operator is considered to be online.
5 seconds are ok if operators have a stable connection to Mibew server. If the server is hosted somewhere outside of your office, it is better to use higher value.
When you leave the "Visitors" page, you go offline.